1. Field of the Invention
The present invention relates generally to in-vehicle navigation systems for displaying map information and current positional information.
2. Related Art
There are various types of in-vehicle navigation systems that display both map information and current positional information. Such a system is disclosed in Japanese Published Examined Patent Application No. Hei 5-32681. The disclosed apparatus detects the travel distance and travel direction of a vehicle on which the apparatus is mounted, obtains a vehicle""s current location from the detected travel distance and travel direction, and shows the map information about the obtained current location and the obtained current location itself on a display unit.
The prior-art in-vehicle navigation apparatus displays the same information when the vehicle is running as the information which is provided when the vehicle is in a stopped state. Therefore, the display unit of the in-vehicle navigation apparatus inevitably supplies more information than necessary for the driver of the vehicle in a running vehicle to get to a destination. This requires time and effort for the driver to properly select only the necessary information from that which is provided on the display unit.
An object of the present invention is to provide an in-vehicle navigation apparatus for displaying appropriate information in accordance with vehicle""s travel states.
In carrying out the invention and according to one aspect thereof, there is provided an in-vehicle navigation apparatus including current positional information generating means for detecting a current location of a vehicle and generating current positional information, map information storage means for storing map information including road information, display map information generating means for reading map information on a predetermined area from the map information storage means on the basis of the current positional information and generating display map information from the map information thus read, and display means for displaying the display map information and the current positional information. The in-vehicle navigation apparatus further includes a travel route planning means for planning a travel route of the vehicle on the basis of the road information, and vehicle speed detecting means for detecting a speed at which the vehicle travels. The display map information generating means changes a size of an extending area which extends along the travel route in accordance with the vehicle speed and extracts map information corresponding to the extending area from the map information read from the map information storage means, thereby providing the display map information.
Namely, according to the present invention, the size of the extending area which extends along a planned travel route to a destination in accordance with the travel speed of a vehicle and the map information corresponding to the changed size of the extending area is displayed. Consequently, only the information is displayed that is necessary for the driver in the running vehicle to get to the destination.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.